3.1. Overview of the Installation Process

First, just a note about re-installations. With Debian, a
circumstance that will require a complete re-installation of your
system is very rare; perhaps mechanical failure of the hard disk would
be the most common case.

Many common operating systems may require a complete installation to
be performed when critical failures take place or for upgrades to new
OS versions. Even if a completely new installation isn't required,
often the programs you use must be re-installed to operate properly in
the new OS.

Under Debian GNU/Linux, it is much more likely that your OS can be repaired
rather than replaced if things go wrong. Upgrades never require a
wholesale installation; you can always upgrade in-place. And the
programs are almost always compatible with successive OS releases. If
a new program version requires newer supporting software, the Debian
packaging system ensures that all the necessary software is
automatically identified and installed. The point is, much effort has
been put into avoiding the need for re-installation, so think of it as
your very last option. The installer is not
designed to re-install over an existing system.

Here's a road map for the steps you will take during the installation
process.

Back up any existing data or documents on the hard disk where you
plan to install.

Gather information about your computer and any needed documentation,
before starting the installation.

If you have problems during the installation, it helps to know which
packages are involved in which steps. Introducing the leading software
actors in this installation drama:

The installer software, debian-installer, is
the primary concern of this manual. It detects hardware and loads
appropriate drivers, uses dhcp-client to set up the
network connection, runs debootstrap to install
the base system packages, and runs tasksel to allow
you to install certain additional software.
Many more actors play smaller parts in this process,
but debian-installer has completed its task when
you load the new system for the first time.

To tune the system to your needs, tasksel allows you
to choose to install various predefined bundles of software like a Web
server or a Desktop environment.

One important option during the installation is whether or not to install
a graphical desktop environment, consisting of the X Window System and
one of the available graphical desktop environments.
If you choose not to select the “Desktop environment” task,
you will only have a relatively basic, command line driven system.
Installing the Desktop environment task is optional because it requires a
fairly large amount of disk space, and because many Debian GNU/Linux systems are
servers which don't really have any need for a graphical user interface
to do their job.

Just be aware that the X Window System is completely separate from
debian-installer, and in fact is much more
complicated. Installation and troubleshooting of the X Window
System is not within the scope of this manual.